Wikipedia tells us that Blues is a music genre and musical form which originated in the Deep South of the United States around the 1870s by African-Americans from roots in African musical traditions, African-American work songs, and spirituals.
Blues as a genre is characterized by its lyrics, bass lines, and instrumentation. Early traditional blues verses consisted of a single line repeated four times. It was only in the first decades of the 20th century that the most common current structure became standard: the AAB pattern, consisting of a line sung over the four first bars.
The Geoff Garbow Band both experiment with and respect these traditions but their vibe is distinctly West London – whether in environmental protest over Heathrow expansion or just singing the blues about life, love and toil.